There are a variety of applications which require synchronized motion between a plurality of components. In such environments, each component is typically referred to as an axis. Movement of an axis may be rotational, linear, or some other more complex motion.
Some applications require one axis to move in response to another axis, such as electronic gearing, or electronic camming operations. In such applications, for example, a motion controller can be used to move a follower axis in response to the position of a master axis.
Many motion controllers provide electronic gearing and camming features in their products. For example, Schneider Automation Modicon motion controllers provide electronic gearing or camming. The 3220/3240 CyberBasic motion controllers also feature both gearing and camming. However, the CyberBasic controllers requires users to position the follower axis in the correct position before turning the camming "on." Other known controllers, such as the QMOT and BMOT single axis controllers, feature electronic gearing but not camming.
Certain problems exist for motion controllers capable of changing modes of operation. As in the CyberBasic motion controllers, users are required to position a follower axis prior to turning a particular mode "on." In other controllers, changing the mode abruptly changed the desired position of the follower axis, which immediately attempted to move to the new mode's desired position. This created a jerk in the movement which could wear or damage the axis.
Prior controllers lack mechanisms for allowing a follower axis to continue to move at a specified rate after a command has been issued to turn the follower mode "off," (command the follower axis to stop responding to the master axis), or to allow the follower mode to be turned "on" while the follower axis is in motion without causing sudden jumps in follower axis position. Furthermore, prior controllers required that out of phase axes be manually adjusted after turning the follower mode "on" in order to synchronize them, or to require the follower mode to be turned on from a follower axis stopped state only.
The present invention provides a motion controller and a method of controlling the motion of a follower axis which does not require a user to position the follower axis prior to turning a mode "on," and which prevents a jerk in movement when changing modes.